Acoustic device



July 25, 1939. R. J. EMMERT ACOUSTIC DEVICE Original Filed Nov. 10, 19303 Sheets-Sheet 1 Rag 9312.] EmmerZ. Q 3 1 ?L, m 115% July 25, 1939. R.J. EMMERT ACOUSTIC DEVICE Original Filed Nov. 10, 1930 3 Sheets-Sheet 2I M E 75R JEmmer Z.

v Ma

y 25, 1939- R. J. EMMERT Rg. 21,159

ACOUSTIC DEVICE Original Filed Nov. 10, 1930 3 Sheets-Sheet 5 74 73 Rodenifl nmarf. I 495a) Reissued July 25, 1939 UNITED STATES PATENT OFFICEACOUSTIG DEVICE Delaware Original No. 2,019,537, dated August 6, 1935,Seriai No. 434,646, November 10, 1930. Application for reissue August14, 1936, Serial No.

2 Claims.

This invention relates to an acoustic device and particularly to anacoustic device having a frustoccnically shaped support having a conicalor frusto-conical diaphragm.

An object of this invention is to improve upon the methods ofmanufacture of the loud speaker so as to produce a loud speaker that issubstantial, rigid, efficient, and economical to produce. This has beenaccomplished by simplifying the construction by reducing the number ofparts to a minimum consistent with skilled workmanship,

reducing the number of operations in the manufacture of the speaker,reducing the amount of labor required and reducing the cost by savingtime, labor, and material.

Another object of this invention is to provide a cone support made fromsheet metal. This has been accomplished by blanking a disc from a pieceof sheet metal, forming an annular channel near the periphery of thedisc, then blanking inwardlyv radiating supporting members or arms fromthe center of the disc and forming or bending these supporting membersso as to cause them to lie in a frusto-conical surface.

Another object of this invention is to improve upon the method ofattaching a diaphragm support to the magnetic frame. This has beenaccomplished by spot welding the supporting arms of the support to themagnetic frame.

Another object of this invention is to improve upon the metallic frame.This has been accomplished by reinforcing the bottom of a cup-shapedhousing for the metallic coil so that there is a tendency to maintain auniform flux density throughout the magnetic path.

Another object of this invention is to improve upon the annular polepiece so as to tend to maintain a substantially uniform flux densitythroughout the annular pole piece and so as to properly distribute theflux in the air gap. This has been accomplished by providing an annularpole piece constructed from two ferro-magnetic annuluses, one of whichhas a maximum diameter equal to the maximum diameter of the cupshapedhousing.

Another object of this invention is to improve upon the method ofassembling the metallic housing. This has been accomplished by weldingthe annular pole piece to the cup-shaped housing 50 so as to eliminatethe conventional fastening means now used, such as screws or rivets.

Another object of this invention is to improve upon the method ofcentering the pole pieces. This has been accomplished by providing acentering jig that holds the annular pole piece concentric with respectto the center pole piece during the welding operation.

Another object of this invention is to improve upon the method ofsupporting the transformer. This has been accomplished by providingsupporting ears integral with adjacent sides of adjacent supporting armsof a diaphragm support so that the transformer may be attached to saidears.

Another object of the invention is to place a terminal board that isconvenient and that requires short leads. This has been accomplished byplacing the terminal board intermediate the transformer and thesupporting ears thereby reducing the length of the input leads.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawings, wherein a preferred embodiment of one form of the presentinvention is clearly shown.

In the drawings:

Fig, 1 discloses a sectional view taken sub stantially on the line Il ofFig. 2 so as to disclose the diaphragm supporting disc.

Fig. 2 is a plan view of the cone supporting disc before the center hasbeen blanked and formed in the center.

Fig. 3 discloses the cone supporting disc after the center has beenblanked.

Fig. 4 discloses the cone support after the inwardly radiatingsupporting arms have been extruded or bent.

Fig. 5 discloses the cone frame structure assembly without the cone themagnet and the annular pole piece in position.

Fig. 6 discloses the assembly after the electromagnetic coil and thepole piece have been assembled but before the centering jig has beenremoved.

Fig. 7 discloses a sectional View of the speaker after being completelyassembled.

Fig. 8 discloses a side view of a cone support showing a terminal blockor board in position looking in the direction of the arrow 8 in Fig. 4.

In the conventional speaker it has been custornary to form the conesupport from a piece of sheet metal by subjecting a circular discprovided with a concentric pole into a frusto-conically shaped supportby a series of dies or forming operations. This requires large heavypresses driven by a large motor consuming much power. Consequently,these large presses are expensive to install, occupy much space and areexpensive to operate.

I have found that a suitable cone support for supporting a diaphragm ofan acoustic device with respect to the electro-magnet may be made bysevering a circular piece II) from a piece of 5 sheet metal and forminga channel [2 near the periphery of the blank or circular piece I as bestseen in Figs. 1 and 2. This may be done by means of a small press. asthe deformation of the channel I2 is relatively small. After this hasbeen done the blank l8 provided with the annular channel I2 is placed ina stamping press that severs the blank along the lines [4, l6 and 18leaving the inwardly extending radial members or arms 28, 2|, 22 and 23.In the same operation the holes 24 are punched in the blank, thefunction of which will appear more clearly later. As best seen in Fig. 3the supports 22 and 23 have been provided with ears or tabs 26, 28, 30and 32 each of which has been provided with apertures 34. The functionof these tabs and apertures will also appear more fully later.

After the blank has been thus formed it is placed in another die thatextrudes or bends the greater portion of the material found in the 93area inclosed by the channel l2 so that this center portion liessubstantially in the surface of a frusto-conical section. The innermostends 36 of the radial supports 20, 2|, 22, and 23 are bent to liesubstantially in the surface of a cylinder so as to snugly fit the outerperiphery of the cup-shaped metallic housing 38. The tabs or feet of theradial supports 20, 2|, 22 and 23 are spot welded at 40 and 42 to theouter periphery of the cupshaped housing 38. This is preferably done ina 35 suitable jig that has not been disclosed for the reason that thejig does not form a part of the invention.

' The magnetic housing 38 is provided with a center pole piece 44riveted thereto at 46. The

40 cross sectional area of the material used in the cup-shaped housing38 is just sufficiently large so that there is substantially the sameflux density in the Walls of the housing as in the center pole piece 44.The reason for doing this 45 is the desirability of using as light amaterial as possible so as to reduce the cost of production and theweight of the magnetic housing. The cost of production is greatlyreduced by an economical use of material and the use of lighter materialrequires smaller presses, less power and lighter dies.

However, when this is done the flux density of the bottom of thecup-shaped housing becomes too great in that the saturation point willbe reached if a suitable fiux density is maintained in the. walls andthe center pole piece. Consequently, in order to reduce the flux densityin the bottom, a reinforcing plate 48 is placed on the bottom of thecup-shaped housing 38 so that the flux density will not becomeexcessive. A further advantage of the reinforcing plate 48 is to give anadditional support to the center pole piece 44 so that the bottom of thecup-shaped housing 33 is not as easily deformed or bent out of shapewhen the speaker unit is jarred or jolted.

The assembly as seen in Fig. 5 is ready for receiving theelectromagnetic or field-producing coil 50 which is inserted in theannular channel found between the outer wall of the cup-shaped housing38 and the. center pole piece 44. The annular pole piece 52 is providedwith the reinforcing member 54 that decreases the flux density near theair gap 56 in much the same I way as the reinforcing plate 48 decreasesthe flux density of the bottom portion of the cup-shaped housing 38. Asthe air gap 56 must be uniform throughout the annular recess or groove,a centering jig 5? is inserted between the annular pole piece 52 and thecenter pole piece 54 during the operation of Welding the annular polepiece 52 to the cup-shaped housing. A packing washer 58 placedintermediate the coil 58 and the annular pole piece 52 retains the coil53 in the position as disclosed in Fig. 6. The annular pole piece 52 isspot welded to the housing 38 in preferably three or four placesthroughout its perimeter.

It can readily be seen that the support In for the diaphragm, thecup-shaped housing 38, the reinforcing plate 48, the center pole piece44, the electromagnetic coil 50, the packing washer 58, and the annularpole piece 52 are all held in a relatively fixed relation as there is nochance for any relative movement between these parts without a failurein the material. Thus it is seen that a speaker assembly has been madethat requires few parts, is light and rigid and is economical in cost.

The assembly shown in Fig. 6 is now ready for the frusto-conicaldiaphragm 60 and the mounting of the transformer 62. The conicaldiaphragm EU in this. particular modification includes a flexible member64, a centering spider 66, a speech coil support 68 and a speech coilwinding 18. The diaphragm assembly 50 has a flexible band or rim 64clamped intermediate the clamping member 12 and the cone support I I.The flexible band 84, the cone support I I and the clamping member 12are held in position by means of the screws 14 which pass through theholes 24 in the support I l and aligned holes in the flexible band andthe clamping member.

As the diaphragm is made from fibrous material it is necessary toprovide an additional support for the apex of the cone. This has beenaccomplished by passing a screw '16 through the spider 66 into athreaded aperture 78 in the center pole piece 44.

A terminal block or board 80 carrying suitable terminals for the leads82 and 84 extending from the coil 58 is attached to the support byeither screws 92 and 94 or other suitable fasteners passing through theholes 34 in the ears 2B, 28, 38 and 32 that are integral with adjacentsupporting arms 22 and 23. Likewise the leads 88, only one of which isshown, extending from the speech coil 10, are attached to the terminalboard 88 .at 88. A transformer 62 is carried by the terminal board 88and rigidly held thereon by the screws 92 and 94.

While the form of embodiment of the present invention as hereindisclosed, constitutes a preferred form, it is to be understood thatother forms might be adopted, all coming within the scope of the claimswhich follow.

What I claim is:

l. A loudspeaker comprising a diaphragm, a magnet structure including acup-shaped magnet member, a supporting member for supporting theperipheral edge of the diaphragm, said supporting member including anannular portion positioned adjacent the peripheral edge of saiddiaphragm and a plurality of arms integral with said annular portion,upturned portions at the free ends of said arms, means for securing saidupturned portions to said cup-shaped member, a transformer supportingmember, and a plurality of lugs on two of said arm portions forsupporting said transformer supporting member.

2. In a loudspeaker having a substantially cone shaped diaphragm and anactuating motor attached thereto, means for supporting the rim of saiddiaphragm which comprises a disc having portions removed from theinterior thereof to form a peripheral shelf on which said rim may rest,and a plurality of inwardly radiating arms, said arms being bentadjacent said junction with said rim to form an enclosure for said cone,the free ends of said arms being bent to extend in a direction parallelto the axis of the cone enclosure, means for securing the free bent 7ends to said actuating motor thereby positioning said cone in properoperating relationship with said motor, two of said arms provided attheir adjacent edges with projecting ears to form supporting means for atransformer.

RODGER J EMMERT.

